<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>环形进度条</title>
</head>
<style>
	* {
	  margin: 0;
	  padding: 0;
	}
	
	body {
	  height: 100vh;
	  display: flex;
	  justify-content: center;
	  align-items: center;
	  background-color: #e8e8e8;
	}
	
	.percent {
	  position: relative;
	  width: 150px;
	  height: 150px;
	}
	
	.percent svg {
	  width: 100%;
	  height: 100%;
	}
	
	.percent svg circle {
	  width: 100%;
	  width: 100%;
	  fill: none;
	  stroke-width: 10;
	  stroke: #000;
	  transform: translate(5px, 5px);
	  stroke-dasharray: 440;
	  stroke-dashoffset: 440;
	  transition: all .5s;
	}
	
	.percent svg circle:nth-child(1) {
	  stroke-dashoffset: 0;
	  stroke: #f3f3f3;
	}
	
	.percent svg circle:nth-child(2) {
	  stroke-dashoffset: calc(440 - 440 * (20 / 100));
	  stroke: #21a0ff;
	}
	
	.percent .number {
	  position: absolute;
	  left: 0;
	  top: 0;
	  width: 100%;
	  height: 100%;
	  display: flex;
	  justify-content: center;
	  align-items: center;
	  color: #333;
	}
	
	.percent .number span:nth-child(1) {
	  font-size: 48px;
	}
	
	.percent .number span:nth-child(2) {
	  font-size: 20px;
	}
</style>
<body>

  <div class="percent">
    <svg>
      <circle cx="70" cy="70" r="70"></circle>
      <circle id="circle" cx="70" cy="70" r="70"></circle>
    </svg>
    <div class="number">
      <h3>
        <span id="percent">20</span>
        <span>%</span>
      </h3>
    </div>
  </div>
  <script src="./环形进度条.js"></script>
</body>
<script>
	let percent = 20
	const percentBox = document.querySelector('#percent')
	const circle = document.querySelector('#circle')
	const timer = setInterval(() => {
	  percent += Math.ceil(Math.random() * 30)
	  if (percent > 100) {
	    percent = 100
	    clearInterval(timer)
	  }
	  percentBox.innerHTML = percent
	  circle.style.strokeDashoffset = `calc(440 - 440 * (${percent} / 100))`
	}, 1500)
</script>
</html>